NUTRIENT AND CARBON CYCLING IN AGRO-ECOSYSTEMS AND THEIR INTERACTIONS WITH ECOSYSTEM SERVICES

摘要

Ecosystem services are the benefits people obtain from ecosystems. An ecosystem is the interacting system of living organisms and their associated non-living environment. Four types of ecosystem services can be distinguished: provisioning services, regulating services, cultural services, and supporting services. In this paper the relationship between agriculture and ecosystem services is described with emphasis on nutrient and carbon cycling in agro-ecosystems. Agriculture can provide the following ecosystem services related to nutrient and carbon cycling: the provision of food and the sequestration and storage of carbon. Strictly speaking it is not agriculture that is providing ecosystem services. It is the soil or natural systems that provide the ecosystem services. Agriculture is a means to produce food and other products. The use of nutrients in agricultural production systems may affect water and air quality through emission of nitrate, ammonia, nitrous oxide and phosphate. Nutrient use also causes carbon dioxide emission to the atmosphere. This implies that nutrient use in agriculture may have a negative effect on the ecosystem services fresh water provision and air quality regulation. Agriculture thus not only delivers ecosystem services, but also ecosystem dis-services. Ecosystem services related to nutrient and carbon cycling in soils are the maintenance of soil fertility and storage of carbon. With erosion, however, nutrients are transported from agricultural fields and they may end up in surface waters. Erosion then is an ecosystem dis-service. Nutrient management strategies should always aim at maximising nutrient use efficiency, whilst minimising the use of scarce resources such as fertile land. Opportunities to maximise nutrient use efficiencies include decreasing nutrient application rates, temporal and spatial matching of nutrient supply and demand, and improving fertiliser recommendations. The ecosystems services delivered by agriculture, and the ecosystem services that are challenged as well as required by agriculture, are as yet not fully appreciated and internalised in the price of products. A better awareness of these services and the attending implications in terms of nutrient and carbon management, is needed for the sake of sustainability.